January 24 Through February 4—TUCSON, ARIZONA: Annual show
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Thu Mar 28, 2024 4:10 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 10 posts ] 
Author Message
 Post subject: Alexandrite on Photo
PostPosted: Fri Apr 13, 2012 5:56 am 
Offline
Valued Contributor
User avatar

Joined: Tue Dec 20, 2005 4:36 am
Posts: 283
Here is another installment of our "Judging Gemstones on Photo".

(Sorry, I forgot to post here last week when it was fresh)

Alexandrite on photo: Better murky than perfect

Color changing Chrysoberyl or Alexandrite is, next to padparadscha, the most faked variety on the internet. The usual trick is to take two photos of a plain chrysoberyl and then, with a click of the mouse, change one photo into red and the other one into green, re-name it “Alexandrite” and raise the price eightfold.

Less scrupulous, but still a scam, is to take a color-shifting Chrysoberyl and tweak the color-shift into a color-change; and then raise the price fourfold.

Finally, when legitimate Alexandrite refuses to be photographed correctly (or somebody dreads the extra work) people may re-produce the actual color-change digitally. Some argue this to be OK in some cases but 100% trust and confidence in the seller is then required. Since such trust is rare the challenge of buying Alexandrite online lays in detecting digital coloring.

Here are some hints:

1. Pure green to pure red color-change has never been found in Alexandrite, much less photographed. If you see such a 100% color change on photo you better move on.

2. Average, yet still expensive, quality Alexandrite will often look blurred on photos. Day-green will be mixed with blue or yellow and/or brown, while purple is diluting the red or is even the dominant color at night. Such quality may still be rightfully called Alexandrite but it needs to backed up by a full gem report including:
a) That it is Alexandrite (not only chrysoberyl)
b) Defining the two colors
c) Judging the degree of change e.g. moderate or strong

Without certificate, photos of Alexandrite are even less conclusive than those of padparadscha or ruby.

As always: Never buy without certificate (aka report).

3. Most traders will (or should) show day and night images. It is good and normal to detect the opposite color (e.g. some red in the green day-light, or some green-blue in the night photo). Exceptions exist but they are amongst the most expensive materials on earth.

4. It is theoretically possible to shot day/night images with two different light sources but 100% identical positioning, and thus identical luster and light pattern in both photos. However, such an identical light pattern in both day and night image are a good reason to suspect digital coloring. Individually shot day and night photos will always show different light pattern.

As far as inclusions, windows, cutting, brilliancy, crystal etc. are concerned Alexandrite is no different from other chrysoberyl.

Questions and comments are welcome.

_________________
Edward Bristol
http://www.WildFishGems.com & http://www.EdwardBristol.com
Exclusively Untreated Gemstones


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Fri Apr 13, 2012 6:55 am 
Offline
Valued Contributor
User avatar

Joined: Tue Jan 29, 2008 8:55 am
Posts: 236
Location: Paris - France
Very instructive and interesting approach! =D>

Thanks Edward!

Best regards,
Christel

_________________
http://christels-jewels.chapso.de/


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Fri Apr 13, 2012 12:04 pm 
Offline
Gemology Online Royal Princess

Joined: Mon Oct 17, 2005 10:56 am
Posts: 6461
Location: The frozen north prairie :-/
Good information, Ed ... thanks! :D

_________________
IIJA Registered Gemologist
GIA Graduate Gemologist


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Sat Apr 14, 2012 5:09 am 
Offline
Valued Contributor
User avatar

Joined: Tue Dec 20, 2005 4:36 am
Posts: 283
Thank you.

It is always a challenge to extract some bullet points from a complex visual sensation.

_________________
Edward Bristol
http://www.WildFishGems.com & http://www.EdwardBristol.com
Exclusively Untreated Gemstones


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Sat Apr 14, 2012 9:42 am 
Offline
Gemology Online Veteran
User avatar

Joined: Thu Feb 22, 2007 10:23 am
Posts: 923
Location: NYC
An alexandrite’s value depends on the hue, tone, and saturation of the two colors it shows and the degree of its color change. The finest alexandrites switch from green to purplish red. At best, however, both hues are medium in saturation. Fine alexandrite’s red looks slightly brownish and its green slightly grayish. Its color-change hues rarely if ever reach the more vivid reds and greens of fine emeralds and rubies.

_________________
Farshid Roshanravan


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Sat Apr 14, 2012 11:29 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
It has been my experience that the modifying tones in fine alex are Bluish green and Purplish red.

I have never seen an unmodified color change: red to green.


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Sat Apr 14, 2012 1:10 pm 
Offline
Site Admin
User avatar

Joined: Fri Apr 17, 2009 3:53 pm
Posts: 2049
Location: Sweden
I have the same experience as Barbra.

_________________
_____________
Conny Forsberg


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Sun Apr 15, 2012 2:31 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Sun Dec 30, 2007 12:01 am
Posts: 556
Location: Vancouver, Canada
Edward Bristol wrote:
As far as inclusions, windows, cutting, brilliancy, crystal etc. are concerned Alexandrite is no different from other Beryl’s.


I hope that was a typo and you meant other "Chrysoberyl"

Tony.

_________________
www.thegemdoctor.com
Beautiful British Columbia


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Mon Apr 16, 2012 4:33 am 
Offline
Valued Contributor
User avatar

Joined: Tue Dec 20, 2005 4:36 am
Posts: 283
Tony, yes, very true, not a typo though but the end of the day. shall be corrected.

_________________
Edward Bristol
http://www.WildFishGems.com & http://www.EdwardBristol.com
Exclusively Untreated Gemstones


Top
 Profile  
Reply with quote  
 Post subject: Re: Alexandrite on Photo
PostPosted: Mon Apr 16, 2012 11:44 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
Edward Bristol wrote:
Tony, yes, very true, not a typo though but the end of the day. shall be corrected.

Done. :D


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 14 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock